Use just X server display number in shm.id filename, instead of full …

…$DISPLAY

Full $DISPLAY is ambiguous - for example :0 and :0.0 means the same. And
indeed X server cmdline contains ":0", while $DISPLAY - ":0.0". So, get
only display number to get the same value regardless of the format. This
also get rid of ":" from the filename for aesthetic reasons.

Fixes "Use shm.id.$DISPLAY to allow more than single X server"

gui-daemon/xside.c

@@ -3195,6 +3195,7 @@ int main(int argc, char **argv)
     char cmd_tmp[256];
     struct stat stat_buf;
     char *display_str;
+    int display_num;
 
     load_default_config_values(&ghandles);
     /* get the VM name to read the right section in config file */
@@ -3230,8 +3231,13 @@ int main(int argc, char **argv)
             fprintf(stderr, "No DISPLAY in environment\n");
             exit(1);
         }
+        if (sscanf(display_str, ":%d.%*d", &display_num) != 1 &&
+                sscanf(display_str, ":%d", &display_num) != 1) {
+            fprintf(stderr, "DISPLAY parse error, expected format like :0 or :0.0\n");
+            exit(1);
+        }
         snprintf(shmid_filename, SHMID_FILENAME_LEN,
-             SHMID_FILENAME_PREFIX "%s", display_str);
+             SHMID_FILENAME_PREFIX "%d", display_num);
         f = fopen(shmid_filename, "r");
         if (!f) {
             fprintf(stderr,

shmoverride/shmoverride.c

@@ -171,6 +171,11 @@ void get_display()
         fprintf(stderr, "cmdline DISPLAY parsing failed\n");
         exit(1);
     }
+
+    /* post-processing: drop leading ':' */
+    res = strlen(display_str);
+    for (in_arg = 0; in_arg < res; in_arg++)
+        display_str[in_arg] = display_str[in_arg+1];
 }
 
 int __attribute__ ((constructor)) initfunc()